Shoe manufacturers currently manufacture press knives for leather cutting by a manual method using card templates. Variation of style, width and size means that only one knife of each type is usually required and fashion changes demand a regular flow of knives with new profiles.
One present method of manufacturing press knives employs a `V` block into which a metal blade is bent locally under the action of a foot operated pin or other deflecting device. The operator uses the card template as a visual guide and by creating a number of local bends at discrete points along the blade produces a profile which approximates adequately to the desired smooth shape of the card template. Where particularly acute bends are required, a combination of heat and broaching together with additional tools enables the operator to produce the substantial deformation without cracking the material.
The blade has to be bent through a greater angle than is actually required in order to allow for springback in the material of the blade. This is achieved through experience and skill of the operator and the continuous visual inspection which he provides.
The profile tolerance achievable with this method is typically plus or minus 0.4 millimeters and a knife for a piece such as an in quarter will require approximately 60 discrete bends.
It is an object of the present invention to provide an automated process and apparatus for manufacturing press knives for cutting leather.